A new genus and species of palaeoscolecid worm has been identified from two specimens found in the Burgess Shale-type deposits in Utah, the United States.
Arrakiscolex aasei. Image credit: University of Missouri.
Palaeoscolecida is a group of extinct ecdysozoan worms that existed from the Ealy Cambrian to the Late Silurian period.
These ancient creatures were narrow and long, up to tens of centimeters in length.
They had an annulated trunk ornamented with circular patterns of phosphatic tesselating plates, a layered cuticle, and an armored proboscis.
“This group of animals are extinct, so we don’t see them, or any modern relatives, on the planet today,” said Dr. Jim Schiffbauer, a paleontologist in the Department of Geological Sciences at the University of Missouri.
“We tend to call them ‘worm-like’ because it’s hard to say that they perfectly fit with annelids, priapulids, or any other types of organism on the planet today that we would generally call a worm.”
“But palaeoscolecids have the same general body plan, which in the history of life has been an incredibly successful body plan.”
The newly-identified palaeoscolecid species lived during the Cambrian period, between 504 and 502 million years ago.
Named Arrakiscolex aasei, it had hundreds of tiny (20-30 μm) discoid plates on each annulus (external circular ring).
“The name of the new genus refers to the fictional planet of Arrakis in the novel Dune by Frank Herbert, which is inhabited by a species of armored worm,” the researchers said.
“Arrakiscolex aasei is a pretty cool addition because it expands the number of worm-like things that we know about from 500 million years ago in North America and adds to our global occurrences and diversity of the palaeoscolecids,” Dr. Schiffbauer said.
“At the time, this palaeoscolecid was likely living on an ocean floor,” added Wade Leibach, a graduate teaching assistant in the Department of Geological Sciences at the University of Missouri.
“It is the first known palaeoscolecid discovery in the Marjum Formation of western Utah and that’s important because this represents one of only a few palaeoscolecid taxa in North America.”
“Other examples of this type of fossil have been previously found in much higher abundance on other continents, such as Asia, so we believe this find can help us better understand how we view prehistoric environments and ecologies, such as why different types of organisms are underrepresented or overrepresented in the fossil record.”
“So, this discovery can be viewed from not only the perspective of its significance in North American paleontology, but also broader trends in evolution, paleogeography and paleoecology.”
The discovery is described in a paper published online in the journal Acta Palaeontologica Polonica.
Wade W. Leibach et al. 2021. First palaeoscolecid from the Cambrian (Drumian, Miaolingian) Marjum Formation of western Utah, USA. Acta Palaeontologica Polonica 66; doi: 10.4202/app.00875.2021